Non-invasive imaging is a powerful clinical tool for the early diagnosis, and monitoring of various disease processes. Next generation molecular imaging promises unparalleled opportunities for visualizing pulmonary infection and inflammation since molecular and cellular alterations occur earlier in a pathologic process, than structural changes. This rapidly developing technology has become an essential tool in the field of oncology, with similar potential for pulmonary infectious and inflammatory conditions. In a Mycobacterium tuberculosis infection model of macrophage-associated pulmonary inflammation, we have demonstrated that [125I]DPA-713, a novel imaging probe, accumulates in M. tuberculosis-induced inflammatory lesions in the lungs of infected mice. [125/4I]DPA-713 has several promising features as a pulmonary imaging agent: a) low molecular weight with excellent penetration into diseased tissues; b) specific mechanism-based tracer, targeting translocator protein (TSPO) in activated macrophages; c) can be labeled with different radioiodine isotopes (PET or SPECT) with short or long half-lives; d) excellent pharmacokinetic profile in lung tissues and; e) importantly, high target-to-non-target ratios for sensitive detectin of macrophage-associated pulmonary inflammation in pre-clinical models. Our central hypothesis is that iodo- DPA-713 is selectively retained by activated macrophages in pulmonary lesions and would therefore serve as a more specific imaging biomarker for real-time evaluation of macrophage-associated inflammation in lung tissues. We propose a multi-disciplinary collaboration, specifically responsive to this RFA for developing probes for activated macrophages and to develop software to process, quantify and correlate in vivo imaging data. We will focus on the following three objectives: 1) validate [125/4I]DPA-713-SPECT/ PET as a biomarker for serial monitoring of macrophage-associated pulmonary inflammation; 2) perform toxicology studies and current Good Manufacturing Practice (cGMP) synthesis for iodo-DPA-713; 3) develop and use computer-assisted image analysis tools for pulmonary disease. The overall goal is to have a fully validated probe ready for human administration and to file a FDA Investigational New Drug (IND) application at the end of the funding period. All tools developed in this proposal are directly translatable to humans, and will be broadly applicable to other macrophage-associated pulmonary infectious or inflammatory conditions.